what size diode do I need

[rockfla]

I know Rockfla said ONE more time, but it's been bugging me. I understand the concept of bypassing the resistor wire or ballast with a jumper. But how is voltage maintained at the coil? The battery voltage is going to be drawn down with the load when the starter is engaged. A diode isn't going to maintain it at 6volts.
Lets say your battery reads 6.4 volts no load.Hit the starter button, starter engages. The battery is going to read say for argument sake 5.9 volts. The coil is going to see 5.9 volts.

A DuckDuckGo search, I don't use goggle anymore, did not show any results.

Direct wire from a "secondary" 6V battery!! OR a dedicated battery for the coil ONLY!!

 

[Mart]

I know Rockfla said ONE more time, but it's been bugging me. I understand the concept of bypassing the resistor wire or ballast with a jumper. But how is voltage maintained at the coil? The battery voltage is going to be drawn down with the load when the starter is engaged. A diode isn't going to maintain it at 6volts.
Lets say your battery reads 6.4 volts no load.Hit the starter button, starter engages. The battery is going to read say for argument sake 5.9 volts. The coil is going to see 5.9 volts.

A DuckDuckGo search, I don't use goggle anymore, did not show any results.

Here's how it works.
Numbers are for illustrative purposes only.
lets say you have 6V at the battery.
You use a resistor to knock that down to 4V at the coil.

You engage the starter the starter pulls the battery voltage down to 5V lets say.
The resistor drops that 5V to lets say 3.5V at the coil.
Hard starty.

So lets put in a diode or relay to bypass the resistor when starting.

Starter pulls battery down to 5V
Coil gets full battery volts which is 5V and more than the normal 4V.
That's better than 3.5V.
Easy starty.

Mart.

 

[Jack E/NJ]

>>>So lets put in a diode or relay to bypass the resistor when starting.>>> Starter pulls battery down to 5V Coil gets full battery volts which is 5V>>>


The relay yields 5v. The diode only yields 4.4v cuz it needs ~0.6v forward bias to make it conduct. Easy starty only if there's a decent spark. 8^)

 

[Don T]

So can it be safely said that the "bypass with a diode" approach is ONLY effective on a ignition system which has a resistor in line to the coil but does NOT have a resistor bypass incorporated in the starting system. I believe this is where the confusion comes in the discussion.

 

[solidaxle]

Hang on partners. We're are talking about two different sources in different posts.


rockfla is saying two batteries in post #41.

Mart I think, is using one battery, correct?

 

[solidaxle]

So can it be safely said that the "bypass with a diode" approach is ONLY effective on a ignition system which has a resistor in line to the coil but does NOT have a resistor bypass incorporated in the starting system. I believe this is where the confusion comes in the discussion.

Don T

That's the way I see it. This would be for a 12 volts system. With a single battery 6 volt system you don't need a resistor in the primary coil circuit to keep the point spark down.

 

[Jack E/NJ]

>>>With a single battery 6 volt system you don't need a resistor in the primary coil circuit to keep the point spark down.>>>


Yes & no.


Yes. No resistor needed with 6v coil.


No, Resistor needed with 4v coil.


8^)

 

[Mart]

So can it be safely said that the "bypass with a diode" approach is ONLY effective on a ignition system which has a resistor in line to the coil but does NOT have a resistor bypass incorporated in the starting system. I believe this is where the confusion comes in the discussion.

Yes that is right.

 

[Mart]

Hang on partners. We're are talking about two different sources in different posts.


rockfla is saying two batteries in post #41.

Mart I think, is using one battery, correct?

I was describing the principle used in a stock type situation that uses this sold start bypass system. One battery with the bypass normally provided by the starter solenoid.

 

[Mart]

>>>With a single battery 6 volt system you don't need a resistor in the primary coil circuit to keep the point spark down.>>>


Yes & no.


Yes. No resistor needed with 6v coil.


No, Resistor needed with 4v coil.


8^)

Yes also correct.

Personally I'm a 12V guy and all my cars use a 12V coil, no resistor and no need for any fancy bypass circuitry.

Mart.